A Dataset represents a view of a the data in a database, constrained by specific parameters such as filtering conditions, order, etc. Datasets can be used to create, retrieve, update and delete records.
Query results are always retrieved on demand, so a dataset can be kept around and reused indefinitely:
my_posts = DB[:posts].filter(:author => 'david') # no records are retrieved p my_posts.all # records are now retrieved ... p my_posts.all # records are retrieved again
In order to provide this functionality, dataset methods such as where, select, order, etc. return modified copies of the dataset, so you can use different datasets to access data:
posts = DB[:posts]
davids_posts = posts.filter(:author => 'david')
old_posts = posts.filter('stamp < ?', Date.today - 7)
Datasets are Enumerable objects, so they can be manipulated using any of the Enumerable methods, such as map, inject, etc.
Some methods are added via metaprogramming:
| COLUMN_CHANGE_OPTS | = | [:select, :sql, :from, :join].freeze | The dataset options that require the removal of cached columns if changed. | |
| DATASET_CLASSES | = | [] | Array of all subclasses of Dataset | |
| MUTATION_METHODS | = | %w'add_graph_aliases and distinct exclude exists filter from from_self full_outer_join graph group group_and_count group_by having inner_join intersect invert join left_outer_join limit naked or order order_by order_more paginate query reject reverse reverse_order right_outer_join select select_all select_more set_defaults set_graph_aliases set_model set_overrides sort sort_by unfiltered union unordered where'.collect{|x| x.to_sym} | All methods that should have a ! method added that modifies the receiver. | |
| NOTIMPL_MSG | = | "This method must be overridden in Sequel adapters".freeze | ||
| STOCK_TRANSFORMS | = | { :marshal => [ # for backwards-compatibility we support also non-base64-encoded values. proc {|v| Marshal.load(v.unpack('m')[0]) rescue Marshal.load(v)}, proc {|v| [Marshal.dump(v)].pack('m')} | ||
| COMMA_SEPARATOR | = | ', '.freeze | ||
| COUNT_OF_ALL_AS_COUNT | = | SQL::Function.new(:count, '*'.lit).as(:count) | ||
| PREPARED_ARG_PLACEHOLDER | = | '?'.lit.freeze | ||
| AND_SEPARATOR | = | " AND ".freeze | ||
| BOOL_FALSE | = | "'f'".freeze | ||
| BOOL_TRUE | = | "'t'".freeze | ||
| COLUMN_REF_RE1 | = | /\A([\w ]+)__([\w ]+)___([\w ]+)\z/.freeze | ||
| COLUMN_REF_RE2 | = | /\A([\w ]+)___([\w ]+)\z/.freeze | ||
| COLUMN_REF_RE3 | = | /\A([\w ]+)__([\w ]+)\z/.freeze | ||
| COUNT_FROM_SELF_OPTS | = | [:distinct, :group, :sql, :limit, :compounds] | ||
| DATE_FORMAT | = | "DATE '%Y-%m-%d'".freeze | ||
| N_ARITY_OPERATORS | = | ::Sequel::SQL::ComplexExpression::N_ARITY_OPERATORS | ||
| NULL | = | "NULL".freeze | ||
| QUESTION_MARK | = | '?'.freeze | ||
| STOCK_COUNT_OPTS | = | {:select => ["COUNT(*)".lit], :order => nil}.freeze | ||
| SELECT_CLAUSE_ORDER | = | %w'distinct columns from join where group having compounds order limit'.freeze | ||
| TIMESTAMP_FORMAT | = | "TIMESTAMP '%Y-%m-%d %H:%M:%S'".freeze | ||
| TWO_ARITY_OPERATORS | = | ::Sequel::SQL::ComplexExpression::TWO_ARITY_OPERATORS | ||
| WILDCARD | = | '*'.freeze |
| inner_join | -> | join |
| db | [RW] | The database that corresponds to this dataset |
| identifier_input_method | [RW] | Set the method to call on identifiers going into the database for this dataset |
| identifier_output_method | [RW] | Set the method to call on identifiers coming the database for this dataset |
| opts | [RW] | The hash of options for this dataset, keys are symbols. |
| quote_identifiers | [W] | Whether to quote identifiers for this dataset |
| row_proc | [RW] | The row_proc for this database, should be a Proc that takes a single hash argument and returns the object you want to fetch_rows to return. |
The array of dataset subclasses.
# File lib/sequel_core/dataset.rb, line 116
116: def self.dataset_classes
117: DATASET_CLASSES
118: end
Setup mutation (e.g. filter!) methods. These operate the same as the non-! methods, but replace the options of the current dataset with the options of the resulting dataset.
# File lib/sequel_core/dataset.rb, line 123
123: def self.def_mutation_method(*meths)
124: meths.each do |meth|
125: class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end")
126: end
127: end
Add the subclass to the array of subclasses.
# File lib/sequel_core/dataset.rb, line 130
130: def self.inherited(c)
131: DATASET_CLASSES << c
132: end
Constructs a new instance of a dataset with an associated database and options. Datasets are usually constructed by invoking Database methods:
DB[:posts]
Or:
DB.dataset # the returned dataset is blank
Sequel::Dataset is an abstract class that is not useful by itself. Each database adaptor should provide a descendant class of Sequel::Dataset.
# File lib/sequel_core/dataset.rb, line 103
103: def initialize(db, opts = nil)
104: @db = db
105: @quote_identifiers = db.quote_identifiers? if db.respond_to?(:quote_identifiers?)
106: @identifier_input_method = db.identifier_input_method if db.respond_to?(:identifier_input_method)
107: @identifier_output_method = db.identifier_output_method if db.respond_to?(:identifier_output_method)
108: @opts = opts || {}
109: @row_proc = nil
110: @transform = nil
111: end
Adds the give graph aliases to the list of graph aliases to use, unlike set_graph_aliases, which replaces the list. See set_graph_aliases.
# File lib/sequel_core/object_graph.rb, line 167
167: def add_graph_aliases(graph_aliases)
168: ds = select_more(*graph_alias_columns(graph_aliases))
169: ds.opts[:graph_aliases] = (ds.opts[:graph_aliases] || {}).merge(graph_aliases)
170: ds
171: end
Returns an array with all records in the dataset. If a block is given, the array is iterated over after all items have been loaded.
# File lib/sequel_core/dataset.rb, line 150
150: def all(opts = nil, &block)
151: a = []
152: each(opts) {|r| a << r}
153: post_load(a)
154: a.each(&block) if block
155: a
156: end
Adds an further filter to an existing filter using AND. If no filter exists an error is raised. This method is identical to filter except it expects an existing filter.
# File lib/sequel_core/dataset/sql.rb, line 23
23: def and(*cond, &block)
24: raise(Error::NoExistingFilter, "No existing filter found.") unless @opts[:having] || @opts[:where]
25: filter(*cond, &block)
26: end
Returns the average value for the given column.
# File lib/sequel_core/dataset/convenience.rb, line 18
18: def avg(column)
19: get(SQL::Function.new(:avg, column))
20: end
For the given type (:select, :insert, :update, or :delete), run the sql with the bind variables specified in the hash. values is a hash of passed to insert or update (if one of those types is used), which may contain placeholders.
# File lib/sequel_core/dataset/prepared_statements.rb, line 181
181: def call(type, bind_variables={}, values=nil)
182: prepare(type, nil, values).call(bind_variables)
183: end
SQL fragment for specifying given CaseExpression.
# File lib/sequel_core/dataset/sql.rb, line 39
39: def case_expression_sql(ce)
40: sql = '(CASE '
41: sql << "#{literal(ce.expression)} " if ce.expression
42: ce.conditions.collect{ |c,r|
43: sql << "WHEN #{literal(c)} THEN #{literal(r)} "
44: }
45: sql << "ELSE #{literal(ce.default)} END)"
46: end
Returns a new clone of the dataset with with the given options merged. If the options changed include options in COLUMN_CHANGE_OPTS, the cached columns are deleted.
# File lib/sequel_core/dataset.rb, line 161
161: def clone(opts = {})
162: c = super()
163: c.opts = @opts.merge(opts)
164: c.instance_variable_set(:@columns, nil) if opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
165: c
166: end
Returns the columns in the result set in their true order. If the columns are currently cached, returns the cached value. Otherwise, a SELECT query is performed to get a single row. Adapters are expected to fill the columns cache with the column information when a query is performed. If the dataset does not have any rows, this will be an empty array. If you are looking for all columns for a single table, see Schema::SQL#schema.
# File lib/sequel_core/dataset.rb, line 174
174: def columns
175: return @columns if @columns
176: ds = unfiltered.unordered.clone(:distinct => nil)
177: ds.single_record
178: @columns = ds.instance_variable_get(:@columns)
179: @columns || []
180: end
SQL fragment for complex expressions
# File lib/sequel_core/dataset/sql.rb, line 54
54: def complex_expression_sql(op, args)
55: case op
56: when *TWO_ARITY_OPERATORS
57: "(#{literal(args.at(0))} #{op} #{literal(args.at(1))})"
58: when *N_ARITY_OPERATORS
59: "(#{args.collect{|a| literal(a)}.join(" #{op} ")})"
60: when :NOT
61: "NOT #{literal(args.at(0))}"
62: when :NOOP
63: literal(args.at(0))
64: when 'B~''B~'
65: "~#{literal(args.at(0))}"
66: else
67: raise(Sequel::Error, "invalid operator #{op}")
68: end
69: end
Returns the number of records in the dataset.
# File lib/sequel_core/dataset/sql.rb, line 72
72: def count
73: options_overlap(COUNT_FROM_SELF_OPTS) ? from_self.count : single_value(STOCK_COUNT_OPTS).to_i
74: end
Creates a view in the database with the given named based on the current dataset.
# File lib/sequel_core/dataset/schema.rb, line 5 5: def create_view(name) 6: @db.create_view(name, self) 7: end
Add a mutation method to this dataset instance.
# File lib/sequel_core/dataset.rb, line 190
190: def def_mutation_method(*meths)
191: meths.each do |meth|
192: instance_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end")
193: end
194: end
Deletes the records in the dataset. The returned value is generally the number of records deleted, but that is adapter dependent.
# File lib/sequel_core/dataset.rb, line 198
198: def delete(*args)
199: execute_dui(delete_sql(*args))
200: end
Formats a DELETE statement using the given options and dataset options.
dataset.filter{|o| o.price >= 100}.delete_sql #=>
"DELETE FROM items WHERE (price >= 100)"
# File lib/sequel_core/dataset/sql.rb, line 81
81: def delete_sql(opts = nil)
82: opts = opts ? @opts.merge(opts) : @opts
83:
84: return static_sql(opts[:sql]) if opts[:sql]
85:
86: if opts[:group]
87: raise Error::InvalidOperation, "Grouped datasets cannot be deleted from"
88: elsif opts[:from].is_a?(Array) && opts[:from].size > 1
89: raise Error::InvalidOperation, "Joined datasets cannot be deleted from"
90: end
91:
92: sql = "DELETE FROM #{source_list(opts[:from])}"
93:
94: if where = opts[:where]
95: sql << " WHERE #{literal(where)}"
96: end
97:
98: sql
99: end
Iterates over the records in the dataset and returns set. If opts have been passed that modify the columns, reset the column information.
# File lib/sequel_core/dataset.rb, line 204
204: def each(opts = nil, &block)
205: if opts && opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
206: prev_columns = @columns
207: begin
208: _each(opts, &block)
209: ensure
210: @columns = prev_columns
211: end
212: else
213: _each(opts, &block)
214: end
215: self
216: end
Yields a paginated dataset for each page and returns the receiver. Does a count to find the total number of records for this dataset.
# File lib/sequel_core/dataset/pagination.rb, line 16
16: def each_page(page_size, &block)
17: raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
18: record_count = count
19: total_pages = (record_count / page_size.to_f).ceil
20: (1..total_pages).each{|page_no| yield paginate(page_no, page_size, record_count)}
21: self
22: end
Adds an EXCEPT clause using a second dataset object. If all is true the clause used is EXCEPT ALL, which may return duplicate rows.
DB[:items].except(DB[:other_items]).sql #=> "SELECT * FROM items EXCEPT SELECT * FROM other_items"
# File lib/sequel_core/dataset/sql.rb, line 106
106: def except(dataset, all = false)
107: compound_clone(:except, dataset, all)
108: end
Performs the inverse of Dataset#filter.
dataset.exclude(:category => 'software').sql #=>
"SELECT * FROM items WHERE (category != 'software')"
# File lib/sequel_core/dataset/sql.rb, line 114
114: def exclude(*cond, &block)
115: clause = (@opts[:having] ? :having : :where)
116: cond = cond.first if cond.size == 1
117: cond = cond.sql_or if (Hash === cond) || ((Array === cond) && (cond.all_two_pairs?))
118: cond = filter_expr(cond, &block)
119: cond = SQL::BooleanExpression.invert(cond)
120: cond = SQL::BooleanExpression.new(:AND, @opts[clause], cond) if @opts[clause]
121: clone(clause => cond)
122: end
Returns an EXISTS clause for the dataset as a LiteralString.
DB.select(1).where(DB[:items].exists).sql #=> "SELECT 1 WHERE EXISTS (SELECT * FROM items)"
# File lib/sequel_core/dataset/sql.rb, line 128
128: def exists(opts = nil)
129: "EXISTS (#{select_sql(opts)})".lit
130: end
Executes a select query and fetches records, passing each record to the supplied block. The yielded records are generally hashes with symbol keys, but that is adapter dependent.
# File lib/sequel_core/dataset.rb, line 221
221: def fetch_rows(sql, &block)
222: raise NotImplementedError, NOTIMPL_MSG
223: end
Execute the SQL on the database and yield the rows as hashes with symbol keys.
# File lib/sequel_core/adapters/do.rb, line 192
192: def fetch_rows(sql)
193: execute(sql) do |reader|
194: cols = @columns = reader.fields.map{|f| output_identifier(f)}
195: while(reader.next!) do
196: h = {}
197: cols.zip(reader.values).each{|k, v| h[k] = v}
198: yield h
199: end
200: end
201: self
202: end
Returns a copy of the dataset with the given conditions imposed upon it. If the query has been grouped, then the conditions are imposed in the HAVING clause. If not, then they are imposed in the WHERE clause. Filter
filter accepts the following argument types:
filter also takes a block, which should return one of the above argument types, and is treated the same way. If both a block and regular argument are provided, they get ANDed together.
Examples:
dataset.filter(:id => 3).sql #=>
"SELECT * FROM items WHERE (id = 3)"
dataset.filter('price < ?', 100).sql #=>
"SELECT * FROM items WHERE price < 100"
dataset.filter([[:id, (1,2,3)], [:id, 0..10]]).sql #=>
"SELECT * FROM items WHERE ((id IN (1, 2, 3)) AND ((id >= 0) AND (id <= 10)))"
dataset.filter('price < 100').sql #=>
"SELECT * FROM items WHERE price < 100"
dataset.filter(:active).sql #=>
"SELECT * FROM items WHERE :active
dataset.filter{|o| o.price < 100}.sql #=>
"SELECT * FROM items WHERE (price < 100)"
Multiple filter calls can be chained for scoping:
software = dataset.filter(:category => 'software')
software.filter{|o| o.price < 100}.sql #=>
"SELECT * FROM items WHERE ((category = 'software') AND (price < 100))"
See doc/dataset_filters.rdoc for more examples and details.
# File lib/sequel_core/dataset/sql.rb, line 176
176: def filter(*cond, &block)
177: clause = (@opts[:having] ? :having : :where)
178: cond = cond.first if cond.size == 1
179: cond = transform_save(cond) if @transform if cond.is_a?(Hash)
180: cond = filter_expr(cond, &block)
181: cond = SQL::BooleanExpression.new(:AND, @opts[clause], cond) if @opts[clause] && !@opts[clause].blank?
182: clone(clause => cond)
183: end
Returns the first record in the dataset. If a numeric argument is given, it is interpreted as a limit, and then returns all matching records up to that limit. If no argument is passed, it returns the first matching record. If any other type of argument(s) is passed, it is given to filter and the first matching record is returned. If a block is given, it is used to filter the dataset before returning anything.
Examples:
ds.first => {:id=>7}
ds.first(2) => [{:id=>6}, {:id=>4}]
ds.order(:id).first(2) => [{:id=>1}, {:id=>2}]
ds.first(:id=>2) => {:id=>2}
ds.first("id = 3") => {:id=>3}
ds.first("id = ?", 4) => {:id=>4}
ds.first{|o| o.id > 2} => {:id=>5}
ds.order(:id).first{|o| o.id > 2} => {:id=>3}
ds.first{|o| o.id > 2} => {:id=>5}
ds.first("id > ?", 4){|o| o.id < 6} => {:id=>5}
ds.order(:id).first(2){|o| o.id < 2} => [{:id=>1}]
# File lib/sequel_core/dataset/convenience.rb, line 48
48: def first(*args, &block)
49: ds = block ? filter(&block) : self
50:
51: if args.empty?
52: ds.single_record
53: else
54: args = (args.size == 1) ? args.first : args
55: if Integer === args
56: ds.limit(args).all
57: else
58: ds.filter(args).single_record
59: end
60: end
61: end
The first source (primary table) for this dataset. If the dataset doesn‘t have a table, raises an error. If the table is aliased, returns the actual table name, not the alias.
# File lib/sequel_core/dataset/sql.rb, line 189
189: def first_source
190: source = @opts[:from]
191: if source.nil? || source.empty?
192: raise Error, 'No source specified for query'
193: end
194: case s = source.first
195: when Hash
196: s.values.first
197: when Symbol
198: sch, table, aliaz = split_symbol(s)
199: aliaz ? aliaz.to_sym : s
200: else
201: s
202: end
203: end
Returns a copy of the dataset with the source changed.
# File lib/sequel_core/dataset/sql.rb, line 206
206: def from(*source)
207: clone(:from => source)
208: end
Returns a dataset selecting from the current dataset.
ds = DB[:items].order(:name) ds.sql #=> "SELECT * FROM items ORDER BY name" ds.from_self.sql #=> "SELECT * FROM (SELECT * FROM items ORDER BY name)"
# File lib/sequel_core/dataset/sql.rb, line 215
215: def from_self
216: fs = {}
217: @opts.keys.each{|k| fs[k] = nil}
218: fs[:from] = [self]
219: clone(fs)
220: end
Allows you to join multiple datasets/tables and have the result set split into component tables.
This differs from the usual usage of join, which returns the result set as a single hash. For example:
# CREATE TABLE artists (id INTEGER, name TEXT);
# CREATE TABLE albums (id INTEGER, name TEXT, artist_id INTEGER);
DB[:artists].left_outer_join(:albums, :artist_id=>:id).first
=> {:id=>(albums.id||artists.id), :name=>(albums.name||artist.names), :artist_id=>albums.artist_id}
DB[:artists].graph(:albums, :artist_id=>:id).first
=> {:artists=>{:id=>artists.id, :name=>artists.name}, :albums=>{:id=>albums.id, :name=>albums.name, :artist_id=>albums.artist_id}}
Using a join such as left_outer_join, the attribute names that are shared between the tables are combined in the single return hash. You can get around that by using .select with correct aliases for all of the columns, but it is simpler to use graph and have the result set split for you. In addition, graph respects any row_proc or transform attributes of the current dataset and the datasets you use with graph.
If you are graphing a table and all columns for that table are nil, this indicates that no matching rows existed in the table, so graph will return nil instead of a hash with all nil values:
# If the artist doesn't have any albums
DB[:artists].graph(:albums, :artist_id=>:id).first
=> {:artists=>{:id=>artists.id, :name=>artists.name}, :albums=>nil}
Arguments:
# File lib/sequel_core/object_graph.rb, line 48
48: def graph(dataset, join_conditions = nil, options = {}, &block)
49: # Allow the use of a model, dataset, or symbol as the first argument
50: # Find the table name/dataset based on the argument
51: dataset = dataset.dataset if dataset.respond_to?(:dataset)
52: case dataset
53: when Symbol
54: table = dataset
55: dataset = @db[dataset]
56: when ::Sequel::Dataset
57: table = dataset.first_source
58: else
59: raise Error, "The dataset argument should be a symbol, dataset, or model"
60: end
61:
62: # Raise Sequel::Error with explanation that the table alias has been used
63: raise_alias_error = lambda do
64: raise(Error, "this #{options[:table_alias] ? 'alias' : 'table'} has already been been used, please specify " \
65: "#{options[:table_alias] ? 'a different alias' : 'an alias via the :table_alias option'}")
66: end
67:
68: # Only allow table aliases that haven't been used
69: table_alias = options[:table_alias] || table
70: raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)
71:
72: # Join the table early in order to avoid cloning the dataset twice
73: ds = join_table(options[:join_type] || :left_outer, table, join_conditions, :table_alias=>table_alias, :implicit_qualifier=>options[:implicit_qualifier], &block)
74: opts = ds.opts
75:
76: # Whether to include the table in the result set
77: add_table = options[:select] == false ? false : true
78: # Whether to add the columns to the list of column aliases
79: add_columns = !ds.opts.include?(:graph_aliases)
80:
81: # Setup the initial graph data structure if it doesn't exist
82: unless graph = opts[:graph]
83: master = ds.first_source
84: raise_alias_error.call if master == table_alias
85: # Master hash storing all .graph related information
86: graph = opts[:graph] = {}
87: # Associates column aliases back to tables and columns
88: column_aliases = graph[:column_aliases] = {}
89: # Associates table alias (the master is never aliased)
90: table_aliases = graph[:table_aliases] = {master=>self}
91: # Keep track of the alias numbers used
92: ca_num = graph[:column_alias_num] = Hash.new(0)
93: # All columns in the master table are never
94: # aliased, but are not included if set_graph_aliases
95: # has been used.
96: if add_columns
97: select = opts[:select] = []
98: columns.each do |column|
99: column_aliases[column] = [master, column]
100: select.push(column.qualify(master))
101: end
102: end
103: end
104:
105: # Add the table alias to the list of aliases
106: # Even if it isn't been used in the result set,
107: # we add a key for it with a nil value so we can check if it
108: # is used more than once
109: table_aliases = graph[:table_aliases]
110: table_aliases[table_alias] = add_table ? dataset : nil
111:
112: # Add the columns to the selection unless we are ignoring them
113: if add_table && add_columns
114: select = opts[:select]
115: column_aliases = graph[:column_aliases]
116: ca_num = graph[:column_alias_num]
117: # Which columns to add to the result set
118: cols = options[:select] || dataset.columns
119: # If the column hasn't been used yet, don't alias it.
120: # If it has been used, try table_column.
121: # If that has been used, try table_column_N
122: # using the next value of N that we know hasn't been
123: # used
124: cols.each do |column|
125: col_alias, identifier = if column_aliases[column]
126: column_alias = "#{table_alias}_#{column}""#{table_alias}_#{column}"
127: if column_aliases[column_alias]
128: column_alias_num = ca_num[column_alias]
129: column_alias = "#{column_alias}_#{column_alias_num}""#{column_alias}_#{column_alias_num}"
130: ca_num[column_alias] += 1
131: end
132: [column_alias, column.qualify(table_alias).as(column_alias)]
133: else
134: [column, column.qualify(table_alias)]
135: end
136: column_aliases[col_alias] = [table_alias, column]
137: select.push(identifier)
138: end
139: end
140: ds
141: end
Pattern match any of the columns to any of the terms. The terms can be strings (which use LIKE) or regular expressions (which are only supported in some databases). See Sequel::SQL::StringExpression.like. Note that the total number of pattern matches will be cols.length * terms.length, which could cause performance issues.
# File lib/sequel_core/dataset/sql.rb, line 233
233: def grep(cols, terms)
234: filter(SQL::BooleanExpression.new(:OR, *Array(cols).collect{|c| SQL::StringExpression.like(c, *terms)}))
235: end
Returns a copy of the dataset with the having conditions changed. Raises an error if the dataset has not been grouped. See also filter.
# File lib/sequel_core/dataset/sql.rb, line 246
246: def having(*cond, &block)
247: raise(Error::InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group]
248: clone(:having=>{}).filter(*cond, &block)
249: end
Inserts values into the associated table. The returned value is generally the value of the primary key for the inserted row, but that is adapter dependent.
# File lib/sequel_core/dataset.rb, line 227
227: def insert(*values)
228: execute_insert(insert_sql(*values))
229: end
Inserts multiple values. If a block is given it is invoked for each item in the given array before inserting it. See multi_insert as a possible faster version that inserts multiple records in one SQL statement.
# File lib/sequel_core/dataset/sql.rb, line 255
255: def insert_multiple(array, &block)
256: if block
257: array.each {|i| insert(block[i])}
258: else
259: array.each {|i| insert(i)}
260: end
261: end
Formats an INSERT statement using the given values. If a hash is given, the resulting statement includes column names. If no values are given, the resulting statement includes a DEFAULT VALUES clause.
dataset.insert_sql() #=> 'INSERT INTO items DEFAULT VALUES'
dataset.insert_sql(1,2,3) #=> 'INSERT INTO items VALUES (1, 2, 3)'
dataset.insert_sql(:a => 1, :b => 2) #=>
'INSERT INTO items (a, b) VALUES (1, 2)'
# File lib/sequel_core/dataset/sql.rb, line 271
271: def insert_sql(*values)
272: return static_sql(@opts[:sql]) if @opts[:sql]
273:
274: from = source_list(@opts[:from])
275: case values.size
276: when 0
277: values = {}
278: when 1
279: vals = values.at(0)
280: if vals.is_one_of?(Hash, Dataset, Array)
281: values = vals
282: elsif vals.respond_to?(:values)
283: values = vals.values
284: end
285: end
286:
287: case values
288: when Array
289: if values.empty?
290: insert_default_values_sql
291: else
292: "INSERT INTO #{from} VALUES #{literal(values)}"
293: end
294: when Hash
295: values = @opts[:defaults].merge(values) if @opts[:defaults]
296: values = values.merge(@opts[:overrides]) if @opts[:overrides]
297: values = transform_save(values) if @transform
298: if values.empty?
299: insert_default_values_sql
300: else
301: fl, vl = [], []
302: values.each do |k, v|
303: fl << literal(String === k ? k.to_sym : k)
304: vl << literal(v)
305: end
306: "INSERT INTO #{from} (#{fl.join(COMMA_SEPARATOR)}) VALUES (#{vl.join(COMMA_SEPARATOR)})"
307: end
308: when Dataset
309: "INSERT INTO #{from} #{literal(values)}"
310: end
311: end
Adds an INTERSECT clause using a second dataset object. If all is true the clause used is INTERSECT ALL, which may return duplicate rows.
DB[:items].intersect(DB[:other_items]).sql #=> "SELECT * FROM items INTERSECT SELECT * FROM other_items"
# File lib/sequel_core/dataset/sql.rb, line 318
318: def intersect(dataset, all = false)
319: compound_clone(:intersect, dataset, all)
320: end
Inverts the current filter
dataset.filter(:category => 'software').invert.sql #=>
"SELECT * FROM items WHERE (category != 'software')"
# File lib/sequel_core/dataset/sql.rb, line 326
326: def invert
327: having, where = @opts[:having], @opts[:where]
328: raise(Error, "No current filter") unless having || where
329: o = {}
330: o[:having] = SQL::BooleanExpression.invert(having) if having
331: o[:where] = SQL::BooleanExpression.invert(where) if where
332: clone(o)
333: end
SQL fragment specifying a JOIN clause without ON or USING.
# File lib/sequel_core/dataset/sql.rb, line 341
341: def join_clause_sql(jc)
342: table = jc.table
343: table_alias = jc.table_alias
344: table_alias = nil if table == table_alias
345: tref = table_ref(table)
346: " #{join_type_sql(jc.join_type)} #{table_alias ? as_sql(tref, table_alias) : tref}"
347: end
Returns a joined dataset. Uses the following arguments:
# File lib/sequel_core/dataset/sql.rb, line 389
389: def join_table(type, table, expr=nil, options={}, &block)
390: if options.is_one_of?(Symbol, String)
391: table_alias = options
392: last_alias = nil
393: else
394: table_alias = options[:table_alias]
395: last_alias = options[:implicit_qualifier]
396: end
397: if Dataset === table
398: if table_alias.nil?
399: table_alias_num = (@opts[:num_dataset_sources] || 0) + 1
400: table_alias = "t#{table_alias_num}"
401: end
402: table_name = table_alias
403: else
404: table = table.table_name if table.respond_to?(:table_name)
405: table_name = table_alias || table
406: end
407:
408: join = if expr.nil? and !block_given?
409: SQL::JoinClause.new(type, table, table_alias)
410: elsif Array === expr and !expr.empty? and expr.all?{|x| Symbol === x}
411: raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block_given?
412: SQL::JoinUsingClause.new(expr, type, table, table_alias)
413: else
414: last_alias ||= @opts[:last_joined_table] || (first_source.is_a?(Dataset) ? 't1' : first_source)
415: if Hash === expr or (Array === expr and expr.all_two_pairs?)
416: expr = expr.collect do |k, v|
417: k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
418: v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
419: [k,v]
420: end
421: end
422: if block_given?
423: expr2 = yield(table_name, last_alias, @opts[:join] || [])
424: expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
425: end
426: SQL::JoinOnClause.new(expr, type, table, table_alias)
427: end
428:
429: opts = {:join => (@opts[:join] || []) + [join], :last_joined_table => table_name}
430: opts[:num_dataset_sources] = table_alias_num if table_alias_num
431: clone(opts)
432: end
Reverses the order and then runs first. Note that this will not necessarily give you the last record in the dataset, unless you have an unambiguous order. If there is not currently an order for this dataset, raises an Error.
# File lib/sequel_core/dataset/convenience.rb, line 83
83: def last(*args, &block)
84: raise(Error, 'No order specified') unless @opts[:order]
85: reverse.first(*args, &block)
86: end
If given an integer, the dataset will contain only the first l results. If given a range, it will contain only those at offsets within that range. If a second argument is given, it is used as an offset.
# File lib/sequel_core/dataset/sql.rb, line 437
437: def limit(l, o = nil)
438: return from_self.limit(l, o) if @opts[:sql]
439:
440: if Range === l
441: o = l.first
442: l = l.interval + 1
443: end
444: l = l.to_i
445: raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
446: opts = {:limit => l}
447: if o
448: o = o.to_i
449: raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
450: opts[:offset] = o
451: end
452: clone(opts)
453: end
Use the ISO values for dates and times.
# File lib/sequel_core/adapters/jdbc.rb, line 418
418: def literal(v)
419: case v
420: when Time
421: literal(v.iso8601)
422: when Date, DateTime, Java::JavaSql::Timestamp, Java::JavaSql::Date
423: literal(v.to_s)
424: else
425: super
426: end
427: end
Handle the usual time class overrides.
# File lib/sequel_core/adapters/do.rb, line 179
179: def literal(v)
180: case v
181: when Time
182: literal(v.iso8601)
183: when Date, DateTime
184: literal(v.to_s)
185: else
186: super
187: end
188: end
Returns a literal representation of a value to be used as part of an SQL expression.
dataset.literal("abc'def\\") #=> "'abc''def\\\\'"
dataset.literal(:items__id) #=> "items.id"
dataset.literal([1, 2, 3]) => "(1, 2, 3)"
dataset.literal(DB[:items]) => "(SELECT * FROM items)"
dataset.literal(:x + 1 > :y) => "((x + 1) > y)"
If an unsupported object is given, an exception is raised.
# File lib/sequel_core/dataset/sql.rb, line 465
465: def literal(v)
466: case v
467: when LiteralString
468: v
469: when String
470: "'#{v.gsub(/\\/, "\\\\\\\\").gsub(/'/, "''")}'"
471: when Integer, Float
472: v.to_s
473: when BigDecimal
474: d = v.to_s("F")
475: d = "'#{d}'" if v.nan? || v.infinite?
476: d
477: when NilClass
478: NULL
479: when TrueClass
480: BOOL_TRUE
481: when FalseClass
482: BOOL_FALSE
483: when Symbol
484: symbol_to_column_ref(v)
485: when ::Sequel::SQL::Expression
486: v.to_s(self)
487: when Array
488: v.all_two_pairs? ? literal(v.sql_expr) : array_sql(v)
489: when Hash
490: literal(v.sql_expr)
491: when Time, DateTime
492: v.strftime(TIMESTAMP_FORMAT)
493: when Date
494: v.strftime(DATE_FORMAT)
495: when Dataset
496: "(#{subselect_sql(v)})"
497: else
498: raise Error, "can't express #{v.inspect} as a SQL literal"
499: end
500: end
Maps column values for each record in the dataset (if a column name is given), or performs the stock mapping functionality of Enumerable.
# File lib/sequel_core/dataset/convenience.rb, line 90
90: def map(column_name = nil, &block)
91: if column_name
92: super() {|r| r[column_name]}
93: else
94: super(&block)
95: end
96: end
Returns the maximum value for the given column.
# File lib/sequel_core/dataset/convenience.rb, line 99
99: def max(column)
100: get(SQL::Function.new(:max, column))
101: end
Returns the minimum value for the given column.
# File lib/sequel_core/dataset/convenience.rb, line 104
104: def min(column)
105: get(SQL::Function.new(:min, column))
106: end
Returns the the model classes associated with the dataset as a hash. If the dataset is associated with a single model class, a key of nil is used. For datasets with polymorphic models, the keys are values of the polymorphic column and the values are the corresponding model classes to which they map.
# File lib/sequel_core/dataset.rb, line 242
242: def model_classes
243: @opts[:models]
244: end
Inserts multiple records into the associated table. This method can be to efficiently insert a large amounts of records into a table. Inserts are automatically wrapped in a transaction.
This method should be called with a columns array and an array of value arrays:
dataset.multi_insert([:x, :y], [[1, 2], [3, 4]])
This method can also be called with an array of hashes:
dataset.multi_insert({:x => 1}, {:x => 2})
Be aware that all hashes should have the same keys if you use this calling method, otherwise some columns could be missed or set to null instead of to default values.
The method also accepts a :slice or :commit_every option that specifies the number of records to insert per transaction. This is useful especially when inserting a large number of records, e.g.:
# this will commit every 50 records dataset.multi_insert(lots_of_records, :slice => 50)
# File lib/sequel_core/dataset/convenience.rb, line 130
130: def multi_insert(*args)
131: if args.empty?
132: return
133: elsif args[0].is_a?(Array) && args[1].is_a?(Array)
134: columns, values, opts = *args
135: elsif args[0].is_a?(Array) && args[1].is_a?(Dataset)
136: table = @opts[:from].first
137: columns, dataset = *args
138: sql = "INSERT INTO #{quote_identifier(table)} (#{identifier_list(columns)}) VALUES #{literal(dataset)}"
139: return @db.transaction{execute_dui(sql)}
140: else
141: # we assume that an array of hashes is given
142: hashes, opts = *args
143: return if hashes.empty?
144: columns = hashes.first.keys
145: # convert the hashes into arrays
146: values = hashes.map {|h| columns.map {|c| h[c]}}
147: end
148: # make sure there's work to do
149: return if columns.empty? || values.empty?
150:
151: slice_size = opts && (opts[:commit_every] || opts[:slice])
152:
153: if slice_size
154: values.each_slice(slice_size) do |slice|
155: statements = multi_insert_sql(columns, slice)
156: @db.transaction{statements.each{|st| execute_dui(st)}}
157: end
158: else
159: statements = multi_insert_sql(columns, values)
160: @db.transaction{statements.each{|st| execute_dui(st)}}
161: end
162: end
Returns an array of insert statements for inserting multiple records. This method is used by multi_insert to format insert statements and expects a keys array and and an array of value arrays.
This method should be overridden by descendants if the support inserting multiple records in a single SQL statement.
# File lib/sequel_core/dataset/sql.rb, line 508
508: def multi_insert_sql(columns, values)
509: table = quote_identifier(@opts[:from].first)
510: columns = identifier_list(columns)
511: values.map do |r|
512: "INSERT INTO #{table} (#{columns}) VALUES #{literal(r)}"
513: end
514: end
Adds an alternate filter to an existing filter using OR. If no filter exists an error is raised.
# File lib/sequel_core/dataset/sql.rb, line 518
518: def or(*cond, &block)
519: clause = (@opts[:having] ? :having : :where)
520: cond = cond.first if cond.size == 1
521: if @opts[clause]
522: clone(clause => SQL::BooleanExpression.new(:OR, @opts[clause], filter_expr(cond, &block)))
523: else
524: raise Error::NoExistingFilter, "No existing filter found."
525: end
526: end
Returns a copy of the dataset with the order changed. If a nil is given the returned dataset has no order. This can accept multiple arguments of varying kinds, and even SQL functions.
ds.order(:name).sql #=> 'SELECT * FROM items ORDER BY name'
ds.order(:a, :b).sql #=> 'SELECT * FROM items ORDER BY a, b'
ds.order('a + b'.lit).sql #=> 'SELECT * FROM items ORDER BY a + b'
ds.order(:a + :b).sql #=> 'SELECT * FROM items ORDER BY (a + b)'
ds.order(:name.desc).sql #=> 'SELECT * FROM items ORDER BY name DESC'
ds.order(:name.asc).sql #=> 'SELECT * FROM items ORDER BY name ASC'
ds.order(:arr|1).sql #=> 'SELECT * FROM items ORDER BY arr[1]'
ds.order(nil).sql #=> 'SELECT * FROM items'
# File lib/sequel_core/dataset/sql.rb, line 540
540: def order(*order)
541: clone(:order => (order.compact.empty?) ? nil : order)
542: end
Returns a paginated dataset. The returned dataset is limited to the page size at the correct offset, and extended with the Pagination module. If a record count is not provided, does a count of total number of records for this dataset.
# File lib/sequel_core/dataset/pagination.rb, line 7
7: def paginate(page_no, page_size, record_count=nil)
8: raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
9: paginated = limit(page_size, (page_no - 1) * page_size)
10: paginated.extend(Pagination)
11: paginated.set_pagination_info(page_no, page_size, record_count || count)
12: end
Returns the column name for the polymorphic key.
# File lib/sequel_core/dataset.rb, line 253
253: def polymorphic_key
254: @opts[:polymorphic_key]
255: end
Create a named prepared statement that is stored in the database (and connection) for reuse.
# File lib/sequel_core/adapters/jdbc.rb, line 431
431: def prepare(type, name=nil, values=nil)
432: ps = to_prepared_statement(type, values)
433: ps.extend(PreparedStatementMethods)
434: if name
435: ps.prepared_statement_name = name
436: db.prepared_statements[name] = ps
437: end
438: ps
439: end
Prepare an SQL statement for later execution. This returns a clone of the dataset extended with PreparedStatementMethods, on which you can call call with the hash of bind variables to do substitution. The prepared statement is also stored in the associated database. The following usage is identical:
ps = prepare(:select, :select_by_name) ps.call(:name=>'Blah') db.call(:select_by_name, :name=>'Blah')
# File lib/sequel_core/dataset/prepared_statements.rb, line 194
194: def prepare(type, name=nil, values=nil)
195: ps = to_prepared_statement(type, values)
196: db.prepared_statements[name] = ps if name
197: ps
198: end
SQL fragment for the qualifed identifier, specifying a table and a column (or schema and table).
# File lib/sequel_core/dataset/sql.rb, line 567
567: def qualified_identifier_sql(qcr)
568: [qcr.table, qcr.column].map{|x| x.is_one_of?(SQL::QualifiedIdentifier, SQL::Identifier, Symbol) ? literal(x) : quote_identifier(x)}.join('.')
569: end
Translates a query block into a dataset. Query blocks can be useful when expressing complex SELECT statements, e.g.:
dataset = DB[:items].query do
select :x, :y, :z
filter{|o| (o.x > 1) & (o.y > 2)}
order :z.desc
end
Which is the same as:
dataset = DB[:items].select(:x, :y, :z).filter{|o| (o.x > 1) & (o.y > 2)}.order(:z.desc)
Note that inside a call to query, you cannot call each, insert, update, or delete (or any method that calls those), or Sequel will raise an error.
# File lib/sequel_core/dataset/query.rb, line 19
19: def query(&block)
20: copy = clone({})
21: copy.extend(QueryBlockCopy)
22: copy.instance_eval(&block)
23: clone(copy.opts)
24: end
Adds quoting to identifiers (columns and tables). If identifiers are not being quoted, returns name as a string. If identifiers are being quoted quote the name with quoted_identifier.
# File lib/sequel_core/dataset/sql.rb, line 574
574: def quote_identifier(name)
575: return name if name.is_a?(LiteralString)
576: name = input_identifier(name)
577: name = quoted_identifier(name) if quote_identifiers?
578: name
579: end
Whether this dataset quotes identifiers.
# File lib/sequel_core/dataset.rb, line 258
258: def quote_identifiers?
259: @quote_identifiers
260: end
Separates the schema from the table and returns a string with them quoted (if quoting identifiers)
# File lib/sequel_core/dataset/sql.rb, line 584
584: def quote_schema_table(table)
585: schema, table = schema_and_table(table)
586: "#{"#{quote_identifier(schema)}." if schema}#{quote_identifier(table)}"
587: end
This method quotes the given name with the SQL standard double quote. should be overridden by subclasses to provide quoting not matching the SQL standard, such as backtick (used by MySQL and SQLite).
# File lib/sequel_core/dataset/sql.rb, line 592
592: def quoted_identifier(name)
593: "\"#{name.to_s.gsub('"', '""')}\""
594: end
Returns a Range object made from the minimum and maximum values for the given column.
# File lib/sequel_core/dataset/convenience.rb, line 172
172: def range(column)
173: if r = select(SQL::Function.new(:min, column).as(:v1), SQL::Function.new(:max, column).as(:v2)).first
174: (r[:v1]..r[:v2])
175: end
176: end
Split the schema information from the table
# File lib/sequel_core/dataset/sql.rb, line 604
604: def schema_and_table(table_name)
605: sch = db.default_schema if db
606: case table_name
607: when Symbol
608: s, t, a = split_symbol(table_name)
609: [s||sch, t]
610: when SQL::QualifiedIdentifier
611: [table_name.table, table_name.column]
612: when SQL::Identifier
613: [sch, table_name.value]
614: when String
615: [sch, table_name]
616: else
617: raise Error, 'table_name should be a Symbol, SQL::QualifiedIdentifier, SQL::Identifier, or String'
618: end
619: end
Returns a copy of the dataset selecting the wildcard.
# File lib/sequel_core/dataset/sql.rb, line 628
628: def select_all
629: clone(:select => nil)
630: end
Formats a SELECT statement using the given options and the dataset options.
# File lib/sequel_core/dataset/sql.rb, line 640
640: def select_sql(opts = nil)
641: opts = opts ? @opts.merge(opts) : @opts
642: return static_sql(opts[:sql]) if opts[:sql]
643: sql = 'SELECT'
644: select_clause_order.each{|x| send("select_#{x}_sql", sql, opts)}
645: sql
646: end
Set the server for this dataset to use. Used to pick a specific database shard to run a query against, or to override the default SELECT uses :read_only database and all other queries use the :default database.
# File lib/sequel_core/dataset.rb, line 265
265: def server(servr)
266: clone(:server=>servr)
267: end
This allows you to manually specify the graph aliases to use when using graph. You can use it to only select certain columns, and have those columns mapped to specific aliases in the result set. This is the equivalent of .select for a graphed dataset, and must be used instead of .select whenever graphing is used. Example:
DB[:artists].graph(:albums, :artist_id=>:id).set_graph_aliases(:artist_name=>[:artists, :name], :album_name=>[:albums, :name]).first
=> {:artists=>{:name=>artists.name}, :albums=>{:name=>albums.name}}
Arguments:
# File lib/sequel_core/object_graph.rb, line 158
158: def set_graph_aliases(graph_aliases)
159: ds = select(*graph_alias_columns(graph_aliases))
160: ds.opts[:graph_aliases] = graph_aliases
161: ds
162: end
Associates or disassociates the dataset with a model(s). If nil is specified, the dataset is turned into a naked dataset and returns records as hashes. If a model class specified, the dataset is modified to return records as instances of the model class, e.g:
class MyModel
def initialize(values)
@values = values
...
end
end
dataset.set_model(MyModel)
You can also provide additional arguments to be passed to the model‘s initialize method:
class MyModel
def initialize(values, options)
@values = values
...
end
end
dataset.set_model(MyModel, :allow_delete => false)
The dataset can be made polymorphic by specifying a column name as the polymorphic key and a hash mapping column values to model classes.
dataset.set_model(:kind, {1 => Person, 2 => Business})
You can also set a default model class to fall back on by specifying a class corresponding to nil:
dataset.set_model(:kind, {nil => DefaultClass, 1 => Person, 2 => Business})
To make sure that there is always a default model class, the hash provided should have a default value. To make the dataset map string values to model classes, and keep a good default, try:
dataset.set_model(:kind, Hash.new{|h,k| h[k] = (k.constantize rescue DefaultClass)})
# File lib/sequel_core/dataset.rb, line 322
322: def set_model(key, *args)
323: # This code is more verbose then necessary for performance reasons
324: case key
325: when nil # set_model(nil) => no argument provided, so the dataset is denuded
326: @opts.merge!(:naked => true, :models => nil, :polymorphic_key => nil)
327: self.row_proc = nil
328: when Class
329: # isomorphic model
330: @opts.merge!(:naked => nil, :models => {nil => key}, :polymorphic_key => nil)
331: if key.respond_to?(:load)
332: # the class has a values setter method, so we use it
333: self.row_proc = proc{|h| key.load(h, *args)}
334: else
335: # otherwise we just pass the hash to the constructor
336: self.row_proc = proc{|h| key.new(h, *args)}
337: end
338: when Symbol
339: # polymorphic model
340: hash = args.shift || raise(ArgumentError, "No class hash supplied for polymorphic model")
341: @opts.merge!(:naked => true, :models => hash, :polymorphic_key => key)
342: if (hash.empty? ? (hash[nil] rescue nil) : hash.values.first).respond_to?(:load)
343: # the class has a values setter method, so we use it
344: self.row_proc = proc do |h|
345: c = hash[h[key]] || hash[nil] || \
346: raise(Error, "No matching model class for record (#{polymorphic_key} => #{h[polymorphic_key].inspect})")
347: c.load(h, *args)
348: end
349: else
350: # otherwise we just pass the hash to the constructor
351: self.row_proc = proc do |h|
352: c = hash[h[key]] || hash[nil] || \
353: raise(Error, "No matching model class for record (#{polymorphic_key} => #{h[polymorphic_key].inspect})")
354: c.new(h, *args)
355: end
356: end
357: else
358: raise ArgumentError, "Invalid model specified"
359: end
360: self
361: end
Same as select_sql, not aliased directly to make subclassing simpler.
# File lib/sequel_core/dataset/sql.rb, line 649
649: def sql(*args)
650: select_sql(*args)
651: end
Converts a symbol into a column name. This method supports underscore notation in order to express qualified (two underscores) and aliased (three underscores) columns:
ds = DB[:items] :abc.to_column_ref(ds) #=> "abc" :abc___a.to_column_ref(ds) #=> "abc AS a" :items__abc.to_column_ref(ds) #=> "items.abc" :items__abc___a.to_column_ref(ds) #=> "items.abc AS a"
# File lib/sequel_core/dataset/sql.rb, line 668
668: def symbol_to_column_ref(sym)
669: c_table, column, c_alias = split_symbol(sym)
670: qc = "#{"#{quote_identifier(c_table)}." if c_table}#{quote_identifier(column)}"
671: c_alias ? as_sql(qc, c_alias) : qc
672: end
Returns true if the table exists. Will raise an error if the dataset has fixed SQL or selects from another dataset or more than one table.
# File lib/sequel_core/dataset/convenience.rb, line 200
200: def table_exists?
201: raise(Sequel::Error, "this dataset has fixed SQL") if @opts[:sql]
202: raise(Sequel::Error, "this dataset selects from multiple sources") if @opts[:from].size != 1
203: t = @opts[:from].first
204: raise(Sequel::Error, "this dataset selects from a sub query") if t.is_a?(Dataset)
205: @db.table_exists?(t)
206: end
Returns a string in CSV format containing the dataset records. By default the CSV representation includes the column titles in the first line. You can turn that off by passing false as the include_column_titles argument.
This does not use a CSV library or handle quoting of values in any way. If any values in any of the rows could include commas or line endings, you probably shouldn‘t use this.
# File lib/sequel_core/dataset/convenience.rb, line 216
216: def to_csv(include_column_titles = true)
217: n = naked
218: cols = n.columns
219: csv = ''
220: csv << "#{cols.join(COMMA_SEPARATOR)}\r\n" if include_column_titles
221: n.each{|r| csv << "#{cols.collect{|c| r[c]}.join(COMMA_SEPARATOR)}\r\n"}
222: csv
223: end
Returns a hash with one column used as key and another used as value. If rows have duplicate values for the key column, the latter row(s) will overwrite the value of the previous row(s). If the value_column is not given or nil, uses the entire hash as the value.
# File lib/sequel_core/dataset/convenience.rb, line 229
229: def to_hash(key_column, value_column = nil)
230: inject({}) do |m, r|
231: m[r[key_column]] = value_column ? r[value_column] : r
232: m
233: end
234: end
Sets a value transform which is used to convert values loaded and saved to/from the database. The transform should be supplied as a hash. Each value in the hash should be an array containing two proc objects - one for transforming loaded values, and one for transforming saved values. The following example demonstrates how to store Ruby objects in a dataset using Marshal serialization:
dataset.transform(:obj => [
proc {|v| Marshal.load(v)},
proc {|v| Marshal.dump(v)}
])
dataset.insert_sql(:obj => 1234) #=>
"INSERT INTO items (obj) VALUES ('\004\bi\002\322\004')"
Another form of using transform is by specifying stock transforms:
dataset.transform(:obj => :marshal)
The currently supported stock transforms are :marshal and :yaml.
# File lib/sequel_core/dataset.rb, line 389
389: def transform(t)
390: @transform = t
391: t.each do |k, v|
392: case v
393: when Array
394: if (v.size != 2) || !v.first.is_a?(Proc) && !v.last.is_a?(Proc)
395: raise Error::InvalidTransform, "Invalid transform specified"
396: end
397: else
398: unless v = STOCK_TRANSFORMS[v]
399: raise Error::InvalidTransform, "Invalid transform specified"
400: else
401: t[k] = v
402: end
403: end
404: end
405: self
406: end
Adds a UNION clause using a second dataset object. If all is true the clause used is UNION ALL, which may return duplicate rows.
DB[:items].union(DB[:other_items]).sql #=> "SELECT * FROM items UNION SELECT * FROM other_items"
# File lib/sequel_core/dataset/sql.rb, line 684
684: def union(dataset, all = false)
685: compound_clone(:union, dataset, all)
686: end
# File lib/sequel_core/dataset.rb, line 426
426: def upcase_identifiers=(v)
427: @identifier_input_method = v ? :upcase : nil
428: end
Whether this dataset upcases identifiers.
# File lib/sequel_core/dataset.rb, line 431
431: def upcase_identifiers?
432: @identifier_input_method == :upcase
433: end
Updates values for the dataset. The returned value is generally the number of rows updated, but that is adapter dependent.
# File lib/sequel_core/dataset.rb, line 437
437: def update(*args)
438: execute_dui(update_sql(*args))
439: end
Formats an UPDATE statement using the given values.
dataset.update_sql(:price => 100, :category => 'software') #=>
"UPDATE items SET price = 100, category = 'software'"
Accepts a block, but such usage is discouraged.
Raises an error if the dataset is grouped or includes more than one table.
# File lib/sequel_core/dataset/sql.rb, line 708
708: def update_sql(values = {}, opts = nil)
709: opts = opts ? @opts.merge(opts) : @opts
710:
711: return static_sql(opts[:sql]) if opts[:sql]
712:
713: if opts[:group]
714: raise Error::InvalidOperation, "A grouped dataset cannot be updated"
715: elsif (opts[:from].size > 1) or opts[:join]
716: raise Error::InvalidOperation, "A joined dataset cannot be updated"
717: end
718:
719: sql = "UPDATE #{source_list(@opts[:from])} SET "
720: set = if values.is_a?(Hash)
721: values = opts[:defaults].merge(values) if opts[:defaults]
722: values = values.merge(opts[:overrides]) if opts[:overrides]
723: # get values from hash
724: values = transform_save(values) if @transform
725: values.map do |k, v|
726: "#{k.is_one_of?(String, Symbol) ? quote_identifier(k) : literal(k)} = #{literal(v)}"
727: end.join(COMMA_SEPARATOR)
728: else
729: # copy values verbatim
730: values
731: end
732: sql << set
733: if where = opts[:where]
734: sql << " WHERE #{literal(where)}"
735: end
736:
737: sql
738: end
Return true if the dataset has a non-nil value for any key in opts.
# File lib/sequel_core/dataset.rb, line 447
447: def options_overlap(opts)
448: !(@opts.collect{|k,v| k unless v.nil?}.compact & opts).empty?
449: end
Return a cloned copy of the current dataset extended with PreparedStatementMethods, setting the type and modify values.
# File lib/sequel_core/dataset/prepared_statements.rb, line 204
204: def to_prepared_statement(type, values=nil)
205: ps = clone
206: ps.extend(PreparedStatementMethods)
207: ps.prepared_type = type
208: ps.prepared_modify_values = values
209: ps
210: end